cmd/link: fix mode parameter to fallocate on Linux

Fix the mode parameter to fallocate on Linux which is the operation mode
and not the file mode as with os.OpenFile.

Also handle syscall.EINTR.

Fixes #38950

Change-Id: Ieed20d9ab5c8a49be51c9f9a42b7263f394a5261
Reviewed-on: https://go-review.googlesource.com/c/go/+/232805
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Cherry Zhang <[email protected]>
Reviewed-by: Jeremy Faller <[email protected]>

Author: stevenh

src/cmd/link/internal/ld/outbuf_linux.go

@@ -7,5 +7,5 @@ package ld
 import "syscall"
 
 func (out *OutBuf) fallocate(size uint64) error {
-	return syscall.Fallocate(int(out.f.Fd()), outbufMode, 0, int64(size))
+	return syscall.Fallocate(int(out.f.Fd()), 0, 0, int64(size))
 }

src/cmd/link/internal/ld/outbuf_mmap.go

@@ -10,8 +10,12 @@ import (
 	"syscall"
 )
 
-func (out *OutBuf) Mmap(filesize uint64) error {
-	err := out.fallocate(filesize)
+func (out *OutBuf) Mmap(filesize uint64) (err error) {
+	for {
+		if err = out.fallocate(filesize); err != syscall.EINTR {
+			break
+		}
+	}
 	if err != nil {
 		// Some file systems do not support fallocate. We ignore that error as linking
 		// can still take place, but you might SIGBUS when you write to the mmapped